This invention relates to dies for use in manufacturing diecut sheets of cardboard, corrugated paperboard, corrugated plastic or the like, and more particularly to matching male and female stripping dies for use in stripping scrap material away from such diecut sheets.
Containers of many shapes and sizes are commonly manufactured in high-speed diecutting machines in which one or more cutting dies cut the outline and interior shapes of a container out of a sheet of carboard or some corrugated material. A certain amount of scrap material is necessarily formed as a byproduct of the diecutting operation, and this scrap material needs to be removed from the main product portion of the diecut sheet at some point in order for that portion to be folded into a finished container. Some diecutting machines have stripping dies or pins which remove the scrap material from the diecut sheet.
Stripping dies operate in pairs which cooperate to effect the separation of the scrap material from the diecut sheet, one die of the pair being designated female and the other die being designated male on the basis of their relative shapes. Both stripping dies are conventionally made of wood. The female die is fabricated in the same shape as the main product portion of the diecut sheet but is slightly smaller in size than that portion such that all edges of the main product extend beyond the edges of the female die. The female die may include interior through holes and, accordingly, interior edges corresponding to holes in the end product container. Typically, after the sheet has been cut by the cutting die or dies, it is transported to a position overlying the female die, and the male die is forced down over the female die and into contact with the diecut sheet. The male die is fabricated with protruding portions which are forced against the surface of portions of the scrap material to strip the scrap from the main product. The protruding portions have heretofore been fabricated in the form of stripping rails arranged on the male die such that there is a clearance between the rails and all edges of the female die when the male die is forced over the female die. After the stripping operation the main product portion of the diecut sheet is transported to a stacking device or to some other location for further operations such as folding, bundling and shipment.
Conventionally, the male and female stripping dies are made in two completely separate operations, from two separate pieces of wood. The female die is cut in the shape of the cutting die, as described above, and the leftover wood is discarded as scrap. The male die is formed from a base sheet of wood onto which the stripping rails described above are attached by hand, using the female die as a guide, the female die being maintained in a desired alignment with the base sheet by means of dowel pins placed through holes provided in the female die and the base sheet for that purpose. This technique wastes material and consequently increases the overall cost of a die set. The labor cost associated with fabricating a matching set of dies using this technique is also high due to the requirement of hand cutting and placement of a number of stripping rails. Hand placement also results in inaccuracies of placement of the stripping rails which can cause ineffective stripping or even damage to the stripping dies.
Stripping rails also close off a space between the base sheet of the male die and the diecut sheet and thereby could result in a partial vacuum buildup deleteriously affecting the machine operation when the male die is removed after the stripping operation. In the past, holes have had to be cut through the base sheet to prevent the vacuum buildup.